From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E9D82C433E0 for ; Thu, 21 Jan 2021 12:46:33 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 82E65239FF for ; Thu, 21 Jan 2021 12:46:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 82E65239FF Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=marcan.st Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:Subject: From:References:To:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=+QRnmdnKPAtPgPzxJ5RFuAHpX6mNyOUGzboo7IzOGCs=; b=FlcD1sFGx8MsGs67V0Rr9BWEd 5fjHY8Rap3eU8lMGcbFA8ww0X+J5ne6xSlkoEmny0/pPlJTYzKBAkfigBgND+q7wyko5qtt87KceW Nvwp/mvz4yOeV6OH5rPmhtF1BRlXoG9b/76AS4znCBuchMic+8UoYrN6TFJZwds5CLCygnz7G13TQ 4r6YZiCfXd2T+0UyTaoisQdbokrViPDtEGEs0LtQlZ4mx9f/22vaiSlF9m6YAjPyUZCmDdLkOxyIa Tg+23Tk10QmvXTUfIL8gOYXyfWjQhInfGxLXaeh+uRDfV/wh3QbQ23LCh32jP5Y3J0Higjsq5XFCX HTdGLw4Fg==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l2ZKW-0000vg-GX; Thu, 21 Jan 2021 12:44:52 +0000 Received: from marcansoft.com ([2a01:298:fe:f::2] helo=mail.marcansoft.com) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1l2ZKO-0000sW-LL for linux-arm-kernel@lists.infradead.org; Thu, 21 Jan 2021 12:44:46 +0000 Received: from [127.0.0.1] (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: marcan@marcan.st) by mail.marcansoft.com (Postfix) with ESMTPSA id 5D94441F12; Thu, 21 Jan 2021 12:33:49 +0000 (UTC) To: Mohamed Mediouni , Alexander Graf References: <20210120132717.395873-1-mohamed.mediouni@caramail.com> <20210120132717.395873-3-mohamed.mediouni@caramail.com> <94C20F55-D3B8-4349-B26F-9EA8AAEBF639@caramail.com> From: Hector Martin 'marcan' Subject: Re: [RFC PATCH 2/7] arm64: kernel: Add a WFI hook. Message-ID: Date: Thu, 21 Jan 2021 21:33:46 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <94C20F55-D3B8-4349-B26F-9EA8AAEBF639@caramail.com> Content-Language: es-ES X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210121_074444_844874_1A0BBAAE X-CRM114-Status: GOOD ( 13.59 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Catalin Marinas , linux-kernel@vger.kernel.org, Marc Zyngier , Will Deacon , linux-arm-kernel@lists.infradead.org, Stan Skowronek Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org I already mentioned this privately, but for the benefit of the ML: On 21/01/2021 09.48, Mohamed Mediouni wrote: > If we explicitly use the hardware override registers for this, then > we'll be unable to use the deep sleep support provided by wfi on > Apple SoCs later on without touching Apple-specific MSRs. > > Our current policy is to avoid having those modified inside the kernel > at all costs, considering it to be a job for the bootloader instead. I don't think there is any particular reason to do this; the bootloader should be responsible for setting up all the chicken bits that make the CPU work properly, including doing so for all SMP cores before entering the kernel, but that's not the same thing as power management bits. It seems entirely reasonable to me to configure WFI as clockgate only (so it keeps state), not touch this part of kernel code at all, and then in the cpuidle driver (which can come later) just do: - switch to powerdown mode - save state - wfi - restore state - switch to clockgate mode -- Hector Martin "marcan" (marcan@marcan.st) Public Key: https://mrcn.st/pub _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel